This application claims priority from U.K. Patent Application No. GB 9920297.0, filed Aug. 27, 1999.
This invention relates to automotive vehicles and more particularly to materials and components for use in automotive vehicles, particularly as the interior trim for such vehicles, notably the materials used as lining materials for the driver and passenger seating locations in such a vehicle.
The invention relates to a material and article for use as a headliner, i.e. a material and product for lining the region of the driver and passenger compartment roof which is in proximity to the heads of persons traveling in the vehicle and that provides cushioning. Indeed, such materials are the subject of regulations and associated legislation so far as vehicle manufacturers are concerned. In particular, in the U.S. the Federal Motor Vehicle Safety Standard 201 defines particular impact characteristics and requirements for automotive interiors. Similar such regulations exist and/or are being considered in Europe and other countries. Some aspects of the present invention are also, however, applicable outside the field of headliners but in related automotive and other applications.
Automotive headliners for current vehicle operating conditions are required to fulfill several functions. They need to present a cosmetically pleasing surface finish to the vehicle roof inside surface. They are also now required to provide energy management (arising from a requirement to absorb energy upon impact with the headliner by a person""s head). They are also required to provide a degree of acoustic damping in order to reduce noise in the vehicle. In addition, we have discovered that such structures should be of an integrated structure in which the headliner provides a structural function in terms of presenting a unified structure in which the parts of the structure which contribute to the overall energy-management and other functions are integrated into a generally one-piece structure which presents a unitary basis for providing the requisite structures and functions of a headliner.
The requirements for energy management of an automotive interior as a whole (e.g. headliner in combination with roof structure) are specified (at the present time) in Federal Motor Vehicle Safety Standard 201, which is incorporated herein by reference. This standard sets a maximum HIC value (as defined in the standard) which the interior as a whole should comply with. The HIC value for the interior as a whole defines and indicates the impact characteristics and effect of the interior when impacted by an object, e.g., a person""s head.
With regard to these functions and regulations, we mention the following. In principle, a headliner requires a greater degree of energy management ability in those areas of its structure where the vehicle roof structure to which it is attached has the greatest stiffness and rigidity. Such areas are generally located somewhat laterally of the driver and front seat passenger(s), although other regions of the roof may also be particularly stiff or rigid and require a greater degree of energy management. On the other hand, where the vehicle roof structure is less rigid and more able to deflect (an example of which is the more central region of the roof structure of a vehicle in which the less-structurally braced roof panel is able to deflect under impact) the headliner itself does not need to provide a significant energy management level and a headliner which provides a lower energy management quotient can be accepted in such regions. Accordingly, the requirements of a headliner structure which, in an integrated fashion, is required to span the driver/passenger head location region between and including these regions of varying stiffness and rigidity, likewise vary considerably. For example, where the roof structure is the most rigid, the higher energy management requirements are imposed and required for the headliner and these corresponding regions of the headliner should have a corresponding higher or highest ability to absorb energy upon impact or like circumstances in order that the interior as a whole meets the requirements and new regulations.
An example of a prior headliner proposal which provides for energy absorbency is described in International Patent Application WO 97/109050. This proposal suggests the use of a foam material which is impregnated with a hardening compound in order to provide an energy absorbent headliner. It also describes selectively impregnating different areas of the foam forming the headliner with different amounts of hardener in order to selectively vary the energy absorbent properties. It should be noted that a fiberglass reinforcing layer is incorporated with the foam core to provide structural strength.
A further energy absorbent headliner is proposed in EP 0,882,622. This headliner again uses a foam material which is bonded onto a backing, or reinforcing sheet. To provide selected areas, in particular the marginal areas, with improved energy absorbing properties, additional separate foam panels are provided and bonded to the marginal areas of the headliner.
WO 97/32752 discloses a different type of headliner which comprises a plastic honeycomb core as opposed to the foam cores proposed in the above prior patents. The objective of this configuration though is to provide a more easily recyclable headliner structure. Consequently, problems associated with having to trim considerable amounts of excess material from the formed structure in order to produce the required shape of the headliner are addressed by making the headliner material more easily recyclable. It is not apparent from this proposal that energy absorbent properties are provided by this proposed structure or how, or even if, specific areas are provided with different energy absorbent properties. Indeed, this proposal simply states that it provides good strength and acoustic characteristics. Furthermore, such a plastic honeycomb structure described in this proposal would generally be expected, by virtue of the strength and stiffness of the honeycomb structure, to provide little or no energy absorbency. The interior structure proposed is also relatively heavy and costly to produce since the entire uniform structure would be required to have the maximum required level of energy management/absorbency if it is to be adapted to comply with the new regulations and requirements.
It is also mentioned that a large number of conventional prior art headliners currently in use do not provide any significant energy management or absorbent function. Conventionally, headliners for automotive vehicles have been designed to simply provide a decorative function and to provide acoustic insulation.
Other existing proposals for automotive headliners likewise leave something to be desired in terms of efficacy, simplicity of construction, weight and/or ease of installation and/or related cost factors due to their complex construction and wastage involved in their installation, and can be improved.
A desirable object of the present invention is to provide materials and articles applicable to use as automotive headliners, and for analogous uses offering improvements in relation to efficacy and/or, ease of manufacture and/or ease of installation and/or simplicity of structure and/or versatility, efficacy and/or cost, weight and/or improvements generally.
One aspect of an embodiment of the present invention is predicated on the use, to form an automotive headliner and, in particular, an energy absorbent core structure for an automotive headliner or similar, from a material formed by the joining of straw or tube-like polymeric elements into a coherent mass, for example a block or sheet. In such a material, the polymeric tubes are caused to cohere by a suitable process of cohesion, for example heat-welding or thermal fusing. Such materials are not new in themselves. The general manufacturing process to fabricate such materials is thus also not unknown to the person versed in the art. An example of such a material can be obtained from the firm Trauma-lite Limited of Manchester.
The aforesaid materials are initially formed in block or thick sheet format and then, for typical applications, that block or thick sheet is sliced or cut to produce a sheet or the like which can be conveniently used for applications in which the honeycomb format, the flexibility of the material, energy absorbent properties given by the tubular elements, and distinct method of manufacturing the material can be utilized to advantage.
For the purposes of one aspect of the present invention and its particular embodiments, the basic starting material on which this aspect of the method and product is based, as identified above in general terms, and regardless of its basic structure and method of manufacture (as opposed to the changes in these introduced by the invention and its embodiments) will be referred to as xe2x80x9cmaterials of the kind describedxe2x80x9d.
It should be noted that such honeycomb materials, formed from individual tube-like polymeric elements which are fused together into a unitary structural member, differ substantially both in terms of construction, manufacture, and impact absorbing properties and mechanics from conventional foam materials generally used to provide for impact absorption within conventional headliner assemblies. This material can to some degree and in some respects also be contrasted with conventional honeycomb materials which may also be used to form headliner or other trim assemblies and which are generally produced in very different ways. There are however some similarities between a conventional honeycomb and the material of the kind described. Accordingly, while some aspects of the invention, and the preferred arrangement, are related to the specific material of the kind described, the principles once appreciated in relation to this specific material, can be applied to other similar honeycomb materials and such materials can be accordingly adapted along the lines described.
This aspect of the present invention and its embodiments seek (inter alia) to utilize this material, and various advantageous qualities of the material, to provide a particular advantageous application of the material in order to improve significantly the efficiency of manufacture and/or installation and/or effectiveness in use of automotive interior trim components, particularly headliners and the like.
Accordingly, one broad general aspect of the invention is the use of such a material comprising a fused array of tube-like members to provide an energy management element of an automotive trim product, and in particular of a headliner. In such an arrangement, an automotive trim product with the desired and required energy management capabilities is provided by the advantageous utilization of the energy absorbing capabilities of the material of the kind described. In particular, a headliner of a roof assembly of the present invention would preferably cooperate to provide a value of not more than 1,000 HIC(d) thereacross as measured in accordance with Federal Motor Vehicle Safety Standard 201.
A particular feature of an automotive trim product incorporating an energy management core element comprising an array of fused tube-like members, forming a material of the kind described above, is of the array of fused tube-like members having, and being adapted to have, within the same, substantially one-piece, element integral selective regions (or portions) which are adapted to have different levels of energy management.
An energy management element in which integral selective regions (or portions) of the same, substantially one-piece, unitary element have different energy management properties provides a trim product which can match the localized different energy management requirements of the interior. Such a trim product can be contrasted with conventional designs in which the energy management element provides uniform levels of energy management or, to provide different levels of energy management, additional, separate additional energy management elements (e.g. additional foam blocks) are generally added.
Using a material of the kind described within an automotive trim product, and in particular a headliner, the physical properties, notably the degree of stiffness and/or hardness and/or resilience, may (in alternative and secondary embodiments) be varied by varying the physical properties of some of the tubular or straw-like elements of the one-piece unitary fused array and structure. For example, the cross-sectional diameter or major dimension (if not circular), and/or the wall thickness of those tube members, could be varied. Also, by providing a partial or complete filling of material within the internal spaces or voids of the tube members the properties can be altered and selectively adjusted.
In this way, the material of the kind described can be provided with zones or areas of differing resilience and/or compressibility and/or other physical properties within the structure of a one-piece element whereby, by appropriate placement and choice of these zones in which tube-like members with different properties are used, the differing requirements of an automotive interior trim product such as a headliner can be conveniently accommodated in a unitary product element.
Accordingly, under this aspect and embodiment of the invention there is provided a product and a method of making same, for example an automotive headliner which, in a one-piece unitary construction formed from a material of the kind described, there is provided the relative versatility of incorporating in the product zones of differing compressibility (and energy management) and/or other physical properties, in accordance with the many and varying differing design and layout aspects from one automotive vehicle interior to another. Such an ability and possibility is provided, in part, by the use of the material of the kind described. The headliner is accordingly adapted to provide, and provides, a unitary structure with varying degrees of energy management according to the varying requirements from place to place of the interior.
By providing variations of the density and/or other physical properties of the material of the kind described, the advantage is offered of reducing the cost of the material in those locations where such is possible. To put it another way, the honeycomb structure varies from place to place in the product according to the localized requirements thereof, thereby reducing cost and increasing cost-effectiveness. In this regard it should be noted that the material of the kind described, and honeycomb material in general, when configured to provide a high degree of energy management function are costly to produce. Use of separate, distinct sections of material tailored to provide different energy management functions to reduce the costs has the disadvantage of reducing the structural integrity. By using the material of the kind described or similar, and by selectively tailoring the energy management properties in selective regions of the same one-piece unitary integrated element, however, a cost effective product with sufficient structural integrity can be produced.
In particular, according to this aspect, the fused array of tube-like members forming the energy management element may comprise different individual types of tube-like members which are fused together into the unitary fused array. The different types of tube-like members have differing physical properties, and so provide differing levels of energy management capability.
It will be recognized that due to the way in which conventional honeycomb and foam structures are conventionally produced it is not generally possible to, within an integral one-piece unitary structure, use different cell types (corresponding to different tube-like members of the array) and provide selective regions of an integral structure with different physical properties and energy management properties. The relatively new material of the kind described can, however, provide this function since it is formed in a different way from individual tube-like elements which are then fused together to produce a unitary, integral, integrated coherent structure. However, having appreciated the benefits, as described herein, of this aspect in relation to the material of the kind described, the same or analogous principles can be applied and used in conjunction with other similar and/or related honeycomb structured materials and the method of producing such materials altered to incorporate the benefits.
The material of the straw or tubular elements may be chosen by the skilled person according to the requirements of the particular application and in particular the tube-like members in different regions of the array may be of various different polymeric and/or other materials (generally plastics) with or without fillers and extenders and having different properties. Materials to be considered include not only polypropylene but also polycarbonate, polyethylene and polyesters.
Where the hollow or tubular elements which make up the honeycomb structure are to be fully or partially filled in order to alter the properties, then a suitable material may include polyurethane foam (or polymer fibers or other suitable acoustic materials) to serve as such filling. Where the product requires an indicator providing information as to use and extent of use, then it is believed to be technically feasible to include within the product an impact-responsive dyestuff or the like which will produce a visible color change upon the occurrence of a significant impact with the headliner or other article, so that the need for replacement after a vehicle impact or other event may be readily identified.
In another aspect of the invention, which may be used separately or in combination with the above aspect, the energy management element comprising the array of fused tube-like members, comprising a honeycomb-like assembly of the material of the kind described, is molded to shape. In this way these embodiments of the invention are able to produce a dimensionally-accurate molded structure according to the spacial requirements imposed by the dimensions and shape of the vehicle roof structure while nevertheless providing the required energy management functions in terms of an ability to absorb kinetic energy by deflection and/or buckling of the cross-sectional shape of the tubular elements upon impact.
Such use of the inherent energy management properties of the tubular elements in combination with the hitherto unsuspected ability of the material of the kind described to be molded into a coherent structure presenting physical properties usefully different from those of the unmolded sheet material (of tubular elements) represents a significant advance in the art of constructing headliners. Such a molded no-trim headliner structure in itself is a step forward with respect to previous headliner proposals and uses.
In this way the main structure of the product (for example an automotive interior trim product, in particular a headliner) is formed as a molding-to-size of a sheet or the like element of a material of the kind described. By forming a headliner as a pre-molded (to size) product from a material of the kind described there is provided an improved headliner which is better adapted to the physical requirements of the specific automotive interior location and is more efficiently manufactured and installed than the existing resilient materials which are currently used in this specific location, not to mention the fact that these latter materials are used in multi-piece format in order to accommodate the vagaries of the internal structure (including both vehicle strengthening frame elements and the like, and the sheet metal covering). The headliner provided by this embodiment of the invention is molded to the specific shape and size and may include, for example, a suitably shaped and sized pre-formed sun roof opening to accommodate that function where required.
Such an automotive interior trim product, particularly a headliner, is molded to shape and size, and may include suitably in-molded openings such as for a sun roof, and which is in, preferably, one-piece format and requires no, or at least little/minimal (considerably less than with conventional methods), final trimming to-size on assembly.
The molding process enables the production of a unitary structure having the required dimensional characteristics as mentioned above.
Furthermore, and in a further aspect, the molding of the energy management element surprisingly and unexpectedly, has several additional distinct functions and advantages. In particular it has been found that the molding process can be adapted to cause the tubular elements to be permanently deformed in the required locations or zones or regions, so that the uniform cross-sectional shape of the tubular elements is at least in the outer (meaning opposite sides or upper or lower) regions of the headliner permanently deformed so as to change the structure of these tubular elements so that they are caused to have a reduced crushable or deformable cross-section and thereby their energy management function is likewise altered. Accordingly, the molding technique can be arranged and adapted to alter the energy management capability of selective regions of the energy management element as discussed above under the previous aspect of the invention.
Existing research and development shows that the molding alteration of the structure of the coherent mass of tubular elements produces an important change in the structure and energy management function of the tubular elements, whereby they are caused during the molding process to adopt a permanently reduced or changed cross-sectional profile. Generally it is understood that the stiffness of the honeycomb or the like assembly of tubular elements is increased and the slope of the graph of deflection of the structure under load or impact against load or impact is steepened in the direction indicating a higher rate of rise of resistance to actual deflection.
Accordingly, this discovery of the ability of the tubular elements to provide a changed stiffness and energy management function in response to conditions and configurations adopted during molding means that these embodiments of the invention are able to provide not only a molded and integrated headliner having the required dimensional and format/configuration requirements, but also the product can be provided with energy management qualities, which may or may not vary from place to place, in accordance with the particular requirements of the intended use.
Accordingly, one broad aspect of the invention provides a molded headliner structure. The headliner structure is dimensioned and configured, at least in part by the molding operation, to conform to the corresponding dimensional and configuration requirements of a vehicle roof structure.
Another broad aspect of the invention provides a vehicle headliner or the like in which an assembly of tubular elements is molded to vary its physical characteristics such as crushability and/or deformability and/or stiffness or rigidity, according to the local requirements of the configuration of the vehicle roof structure.
Embodiments of the invention may also adopt an approach in which the energy management function of the headliner is varied by providing differing depth of the headliner in terms of differing thickness of the crushable or deformable tubular element cross-sections. In these embodiments such variation of depth may be provided by an approach in which the energy management function is varied by use of the molding technique to modify or reduce the available crushable or deformable aggregate cross-section of the tubular elements, by modification of this latter factor during the molding process of the headliner. Accordingly, the molding technique varies the available crushable depth of the material. Alternatively, the depth can be varied in other ways.
In the regions of higher energy management requirements, these requirements may be met by the provision of a corresponding depth of the energy management element and array of fused tubular elements. The depth (in terms of deflectable or crushable cross-sectional shape) provides the corresponding energy management function. Likewise where a lesser degree of energy management is needed, a lesser depth of crushable or deflectable cross-section of tubular elements is provided.
It has also been found that this molding of the energy management structure to shape it to size and/or the alteration and provision of localized differing energy management properties in a unitary energy management structure is not limited to energy management elements formed from materials of the kind previously described. In particular, the molding technique can similarly and analogously be used to alter the shape and/or energy management properties of any energy management material comprising a coherent structure comprising an array of laterally interconnected tubular or cellular elements. Such molding advantageously provides similar results and advantages. Indeed this molding aspect, as with some of the previously mentioned aspects, can be applied to energy management structures comprising unitary or coherent honeycomb or cellular materials regardless of how the particular material forming the energy management element is initially produced. Accordingly, under this aspect of the invention, an automotive interior trim product comprises an energy management element produced by molding a sheet of honeycomb or other similar cellular type material with the molding operation adapted to vary the localized energy management properties of particular regions of the molded energy management element.
A further aspect of the invention relates to the use of blocks of the material of the kind described which are formed to the desired cross-sectional shape and size so that layers thereof removed, as in effect blanks for molding or other manufacturing steps to produce a headliner of other trim panel, are already suitably sized and shaped. Such can be formed by closely packing the tube-like elements into a suitably shaped former. When the elements packed in the former are fused together then the block of material produced, and the layers sliced therefrom will have a shape corresponding to the former. Consequently, the layers sliced from the block (i.e. the blanks of material) to form the energy management element are of a near net shape as compared to the final headliner shape and dimension. This advantageously results in a reduction of wastage of material and trimming of the energy management element to produce a trim product of the required shape as compared to that conventionally required. Again, this aspect is predicated upon the use of the material of the kind described which is different to, and is fabricated in a very different way to that conventionally used to produce, conventional honeycomb structures or foam members. In particular it is not generally commercially viable to directly produce a structure of such a near net shape without trimming.
Previously proposed headliner structures for automotive use have been based on, for example, polyurethane within a fiberglass envelope wherein the envelope or surface layer or layers contributes significantly to the structural integrity of the headliner as a whole. The material of the kind described used in the embodiments of the present invention offers improved structural integrity in its own right. However, it will be appreciated that by employing cover layers or panels (for example of fiberglass or other material) on one or both sides of the array of fused tube-like elements forming the energy management element, the structural strength can be further improved. Such cover panels or layers could also be provided in selective regions to provide localized structural strengthening. In addition to strengthening, such cover layers or panels provide a more aesthetically pleasing surface and may also improve the acoustic properties. These cover panels or layers may be structurally attached to the fused array of tube-like members to form an I beam type structure. Such attachment may be achieved in a molded product during the molding operation. Alternatively the cover panels or layers may be laminated onto the layers of material (or blanks) sliced from the block.
It will be appreciated and recognized that the above aspects and inventive features can be used and found individually or in combination in embodiments of the invention.